On Thu, Apr 18, 2019 at 04:50:24PM -0400, Scott Mayhew wrote: > On Thu, 18 Apr 2019, J. Bruce Fields wrote: > > > On Thu, Apr 18, 2019 at 09:24:00AM -0400, Scott Mayhew wrote: > > > While trying to track down some issues involving large numbers of > > > delegations being recalled/revoked, I caught the server setting > > > SEQ4_STATUS_CB_PATH_DOWN while the client was actively responding to > > > CB_RECALLs. It turns out that the client had already done a > > > TEST_STATEID and FREE_STATEID for a delegation being recalled by the > > > time it received the CB_RECALL. > > > > That's interesting, thanks! > > > > This exception seems awfully narrow, though. > > > > If we get back any NFS-level error at all, then I think the callback > > channel is working (am I wrong?) > > Correct, if the client replies with either NFS4ERR_DELAY or > NFS4ERR_BAD_STATEID, the server will retry 1 time (see dl_retries). > After that, we fall thru and nfsd4_cb_recall_done() returns -1 which > causes the SEQ4_STATUS_CB_PATH_DOWN flag to be set. > > > and telling the client to set up a new > > one is probably not going to help. The best we can do is probably just > > give up > > That's what the patch is essentially doing. Or are you saying don't > even bother with the checks but still return 1 so we don't set the > SEQ4_STATUS_CB_PATH_DOWN flag? Right, I don't see any point returning -1 (which ends up setting CB_PATH_DOWN) in any case where we get an nfs-level error. If the client got so far as returning an error, then the callback path is working. I'm not sure exactly what errors *should* result in CB_PATH_DOWN, though. ETIMEDOUT, ENOTCONN, EIO? And maybe we should be checking for those in nfsd4_cb_done, and do away with the convention that -1 means CB_PATH_DOWN. I don't think there's a reason individual callback ops would need different rules for when to mark the callback channel down. --b. > > > and let the client deal with the ensuing > > RECALLABLE_STATE_REVOKED flag. > > The client's already dealing with the RECALLABLE_STATE_REVOKED flag, > that's why it sent a TEST_STATEID and FREE_STATEID before it got this > particular CB_RECALL. The idea behind the patch is to not give the > state manager on the client additional work by setting CB_PATH_DOWN when > the callback channel is clearly working... > > -Scott > > > > --b. > > > > > > > > Signed-off-by: Scott Mayhew <smayhew@xxxxxxxxxx> > > > --- > > > fs/nfsd/nfs4state.c | 8 ++++++++ > > > 1 file changed, 8 insertions(+) > > > > > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > > > index 6a45fb00c5fc..e88e429133a8 100644 > > > --- a/fs/nfsd/nfs4state.c > > > +++ b/fs/nfsd/nfs4state.c > > > @@ -3958,6 +3958,14 @@ static int nfsd4_cb_recall_done(struct nfsd4_callback *cb, > > > rpc_delay(task, 2 * HZ); > > > return 0; > > > } > > > + /* > > > + * Race: client may have done a FREE_STATEID before > > > + * receiving the CB_RECALL. > > > + */ > > > + if (dp->dl_stid.sc_type == NFS4_REVOKED_DELEG_STID && > > > + refcount_read(&dp->dl_stid.sc_count) == 1 && > > > + list_empty(&dp->dl_recall_lru)) > > > + return 1; > > > /*FALLTHRU*/ > > > default: > > > return -1; > > > -- > > > 2.17.2
